The two cycle engine was developed by Sir Dugald Clark in 1878.  The first patented two-stroke engine was a vertical twin by Alfred Scoff in 1904. Scott also developed a rotary valve engine in 1912. The Schnuerle ported engine was patented in 1925 and featured two bypass ports (loop scavenging method). In 1957 Walter Kaaden (MZ, E, Germany) added a third transfer port opposite the exhaust port.

Erns Degner defected from East Germany to join Suzuki. 

In the 60's Suzuki and Yamaha won the World Championship using exotic porting and rotary valve developed by DKW and MZ.

Bill Wisniewsk applied the principle of three port, or Schnuerle porting, to a miniature engine and won the 1964 FAI world speed championship.

Yamaha added a pair of auxiliary transfer ports along side the main transfer ports. Dr. Hans added a pair of small auxiliary exhaust ports at the side of the main exhaust port.

Now effectively banned from common Automotive useage by ever increasing clean air legislation. The two stroke produces excellent power to weight ratio which still makes it a good choice for things like small outboard motors and Lawnmovers.

It is very simple and has few moving parts

STAGE ONE OF A TWO-STROKE CYCLE

COMPRESSION STROKE The piston moves toward the spark plug, compressing the fuel mixture in the cylinder. The advancing piston creates a partial vacuum below it, drawing a fresh fuel-and-air charge into the crankcase through the reed valve. The piston wall seals the transfer port and exhaust port shut during this stroke.

STAGE TWO OF A TWO-STROKE CYCLE

POWER STROKE A spark explodes the compressed fuel mixture, causing the piston to recoil and uncover the transfer and exhaust ports. The spent fuel gases are expelled through the exhaust port, pushed out by the fresh charge entering the cylinder through the transfer port.